1. Field of the Invention
The present invention relates to an image display apparatus having a memory for storing character patterns for the graphic display system by way of a bit map memory.
2. Description of the Prior Art
Various code refresh systems have been used in a character display apparatus for use in word processors or the like; however, graphic display also is needed to satisfy a demand for display of a graph or a pattern. There is a bit map refresh system for effecting graphic display and this system is suitable to display a graph or a pattern. However, even in the case of the display of characters, a character pattern has to be developed in a bit map memory, so that the bit map refresh system has a drawback in that the display processing speed is slower than that of a conventional display apparatus of the code refresh system.
This problem is also caused in a personal computer having a display apparatus of the bit map refresh system. To avoid such a drawback, a barrel shifter and a bit mask controller are provided in a CRT interface section, thereby improving the display processing speed. However, in the conventional apparatus, the arrangement of pattern data in a character generator is different from an arrangement of memories in a graphic memory, so that the processing function of a CPU cannot be efficiently utilized. Such a personal computer is disclosed in "PC-100 Technical Manual" regarding the general personal computer PC-100 made by Nippon Electric Co., Ltd.